%I #28 Feb 02 2023 10:23:49

%S 7,67,1255,8407,67039

%N Numbers k such that (13*10^(k-1) - 31)/9 is a plateau prime.

%C Prime versus probable prime status and proofs are given in the author's table.

%C a(6) > 2*10^5. - _Tyler Busby_, Feb 02 2023

%D C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.

%H Patrick De Geest, <a href="http://www.worldofnumbers.com/deplat.htm#pdp141">PDP Reference Table - 141</a>.

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/1/14441.htm#prime">Prime numbers of the form 144...441</a>.

%H <a href="/index/Pri#Pri_rep">Index entries for primes involving repunits</a>.

%F a(n) = A056245(n+1) + 2.

%e k=7 -> (13*10^(7-1) - 31)/9 = 1444441.

%Y Cf. A056245, A082697-A082720.

%K nonn,base,more

%O 1,1

%A _Patrick De Geest_, Apr 13 2003

%E A new PRP term from _Serge Batalov_, Nov 02 2008

%E Edited by _Ray Chandler_, Nov 04 2014